This randomized, double-blind, placebo-controlled parallel arm study will assess efficacy and safety and the effects of taspoglutide on cardiovascular events in patients with inadequately controlled type 2 diabetes mellitus and established cardiovascular disease. Patients will be randomized to receive either taspoglutide subcutaneously (sc) 10mg weekly for 4 weeks followed by 20mg sc weekly, or weekly sc placebo, in addition to background anti-hyperglycemic medication and standard of care treatment for cardiovascular disease. Anticipated time on study treatment is up to 2 years. Target sample size is 2000 patients.